Strengthening Step Motor Lead Attachment

Adhesive attaches wires for improved ruggedness and durability

By Design News Staff – Design News

Motor manufacturers never intend for the lead wires on small motors to be used as a handle, but that does not stop it from occurring. Even if the motor is handled properly, unattached or unsecured wires allow excessive movement and put undue stress on the internal solder connections. When space is not an issue, possible solutions include a grommet or specialty clamp around the wires to hold them in place. For companies that make small and highly-integrated motors such as Lin Engineering, space is a primary concern, and these approaches could increase the frame housing size. The small step motors also make the assembly of a grommet or specialty clamp a tricky proposition at best. A light cure adhesive from Loctite provides an alternate solution.

Designed specifically for high-speed curing, Loctite’s 352 modified acrylic adhesive is fully cured when exposed to ultraviolet (UV) radiation of 365 nm. In a production process, this means UV light exposure for somewhere around 30 to 60 seconds, depending on the intensity of the UV light. In addition to bonding to a variety of surfaces, such as the motor’s housing or stator laminations and wire insulation, the cured form is highly resistant to vibration.

In Lin’s assembly process, an operator uses a hand-held syringe dispenser to manually dispense a bead of the adhesive around the wires attached to the stator winding. The material’s viscosity provides the right consistency by being easy to dispense and avoiding seepage inside the motor. After application, the stator winding assembly travels on a small conveyor system though a UV-cure process for 30 seconds. Without the UV light exposure, the single component adhesive has a long open time. The cured adhesive has proven to be an effective means of securing the leads and preventing wire failures.